206
WILLIAM MACNAE
grains rarely, if ever, enter the gut ; they are sufficiently heavy to fall
to the base of the buccal cavity and be discarded.
This description of feeding techniques will explain the distribution
ia relation to particle size of the species of Uca, of Dotilla, of species of
Cleistostonza and probably of most of the ocypodid gencra which occur
in or near the mangal. The series of figures of maxillipeds of ocypodid
species given by Ono (1965) is suggestive of the fact that each species
of these genera is highly selective in its demands on the substratum.
Macnae (1957) described such differences in two species of Gleistostonaa,
and subsequent examination of their maxillipeds has confirmed that
FIG. 72. Distribution of some ocypoclicl crabs across an estuarine beach in rolation to
(a) relative hcight of the habitat of each above low water mark, and (b) soil
texture arid particle size. ( 1 ) Scopimera globulosa; (2) Uca Zactea; (3) Ilyograpsus
pusilla; (4) U . arcuata,; (5) Macrophthalnius japonicus; (6) Pnrcrcleistostomrt
cristatum; (7) Cleistoma dilatatum. (Redrawn from Ono (1965) with the lcvel of
high water mark and moan sea-level added ; data taken from H.M. Admiralty Tide
Tables, Vol. 111, I’acific Ocean.)
these appendages have an armature of setae suitable for use ox thc
mudbanks they inhabit. These two species, C. edwardsi McLeay and
C. algoense Brnrd. have their parallels in the mangal. C. wardi Rathbun
and C. macneilli in Australia live in mud semi-fluid only to a depth of
about 2 cm and not outside or in more solid or more fluid mud.
Figure 72 taken from Ono (1965) illustrates the distribution of seven
Japanese ocypodid crabs in relation to particle size, duration of exposure
a t spring tides and relative density of population, i.e. the preferred level.
I have superimposed data lines related to npproximatc levels of spring
tides (these have been taken from Admiralty tide tables).
Among these shore dwelling ocypodid crabs thc species of Metaplax
seem to show the beginnings of the transition from being omnivorous
scavengers to more spccialized methods of feeding by filtration tech-
WILLIAM MACNAE
grains rarely, if ever, enter the gut ; they are sufficiently heavy to fall
to the base of the buccal cavity and be discarded.
This description of feeding techniques will explain the distribution
ia relation to particle size of the species of Uca, of Dotilla, of species of
Cleistostonza and probably of most of the ocypodid gencra which occur
in or near the mangal. The series of figures of maxillipeds of ocypodid
species given by Ono (1965) is suggestive of the fact that each species
of these genera is highly selective in its demands on the substratum.
Macnae (1957) described such differences in two species of Gleistostonaa,
and subsequent examination of their maxillipeds has confirmed that
FIG. 72. Distribution of some ocypoclicl crabs across an estuarine beach in rolation to
(a) relative hcight of the habitat of each above low water mark, and (b) soil
texture arid particle size. ( 1 ) Scopimera globulosa; (2) Uca Zactea; (3) Ilyograpsus
pusilla; (4) U . arcuata,; (5) Macrophthalnius japonicus; (6) Pnrcrcleistostomrt
cristatum; (7) Cleistoma dilatatum. (Redrawn from Ono (1965) with the lcvel of
high water mark and moan sea-level added ; data taken from H.M. Admiralty Tide
Tables, Vol. 111, I’acific Ocean.)
these appendages have an armature of setae suitable for use ox thc
mudbanks they inhabit. These two species, C. edwardsi McLeay and
C. algoense Brnrd. have their parallels in the mangal. C. wardi Rathbun
and C. macneilli in Australia live in mud semi-fluid only to a depth of
about 2 cm and not outside or in more solid or more fluid mud.
Figure 72 taken from Ono (1965) illustrates the distribution of seven
Japanese ocypodid crabs in relation to particle size, duration of exposure
a t spring tides and relative density of population, i.e. the preferred level.
I have superimposed data lines related to npproximatc levels of spring
tides (these have been taken from Admiralty tide tables).
Among these shore dwelling ocypodid crabs thc species of Metaplax
seem to show the beginnings of the transition from being omnivorous
scavengers to more spccialized methods of feeding by filtration tech-